Levalbuterol (also known as (R)-albuterol) is a beta agonist useful as a relaxant of smooth muscle tissue, for example in the treatment of bronchospasm in patients suffering from asthma or chronic obstructive pulmonary disease. It is commercially available as a salt, levalbuterol hydrochloride, in a solution formulation adapted for administration by inhalation using a nebuliser and is sold in the United States under the brand name XOPENEX™. A process for the preparation of levalbuterol hydrochloride is described in U.S. Pat. No. 5,545,745. It has been found that crystals of levalbuterol hydrochloride obtained by this process are plate-like in shape and possess properties generally undesirable in a product intended for administration using a metered dose inhaler.
It would be desirable to administer levalbuterol using a metered dose inhaler (MDI).
The particles of active ingredients for delivery into the lungs of patients using an MDI must meet some very demanding criteria. The patient must be able to receive reproducible doses of a safe and effective amount of the particles deep into the lungs. Thus, the particles of the active ingredient must be of a stable, microscopic size within an acceptable distribution range. In particular, they must be resistant to agglomeration into larger particle clusters, and must not change in size or morphology during storage under varying conditions of temperature and relative humidity or in the presence of formulation components, such as carriers or propellants. Preferably they should have an aerodynamically favorable shape, such as a fiber (Crowder T. M., et al., Pharmaceutical Research, Vol. 19. No. 3, March 2002).